This disclosure relates generally to transport refrigeration systems having an on-board diesel engine. More particularly, this disclosure relates to regeneration of a diesel particle filter during operation of the transport refrigeration system.
Fruits, vegetables and other perishable items, including meat, poultry and fish, fresh or frozen, are commonly transported in the cargo box of a truck, a trailer, or in an intermodal container. Accordingly, it is customarily to provide a transport refrigeration system in operative association with the cargo box for cooling the atmosphere within the cargo box. The transport refrigeration system includes a refrigerant vapor compression system, also referred to as a transport refrigeration unit, and an on-board power unit. The refrigerant vapor compression system typically includes a compressor, a condenser, an expansion device and an evaporator serially connected by refrigerant lines in a closed refrigerant circuit in accord with known refrigerant vapor compression cycles. The power unit includes a fuel-fired engine, typically a diesel fueled engine.
In many truck/trailer transport refrigeration systems, the compressor of the transport refrigeration unit is driven by the engine shaft either through a belt/chain drive or by mechanical shaft-to-shaft coupling. Additionally, other components of the transport refrigeration unit, such as condenser fans, evaporator fans and an alternator, may be driven by the engine shaft through a belt/chain drive. More recently, all electric transport refrigeration systems have been developed for truck/trailer applications wherein the engine drives an on-board generator for generating sufficient electrical power to drive an electric motor operatively associated with the compressor of the transport refrigeration unit. With respect to intermodal containers, clip-on power units, commonly referred to as generator sets or gensets, are available for mounting to the intermodal container, typically when the container is being transported by road or rail, to provide electrical power for operating the compressor drive motor of the transport refrigeration unit associated with the container. The genset includes a diesel engine and a generator driven by the diesel engine.
Although diesel engines function well in powering transport refrigerant systems, diesel engines produce exhaust gases that contain noxious emissions including carbon monoxide, oxides of nitrogen, unburned hydrocarbons and particulate matter. Diesel exhaust treatment units have been developed to reduce the emissions of carbon monoxide, unburned hydrocarbons and particulate matter emitted to the atmosphere. One type of diesel exhaust treatment unit is an in-line exhaust treatment unit that is installed in the exhaust pipe downstream of the engine exhaust manifold and includes a diesel oxidation catalyst and a diesel particulate filter disposed in series.
For example, U.S. Patent Application Publication No. US 2007/0283681 A1 discloses an in-line diesel exhaust treatment device including a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF) disposed in series. The DOC is operative to oxidize carbon monoxide to carbon dioxide, to oxidize unburned hydrocarbons to water and carbon dioxide, and to oxide nitrogen oxide (NO) to nitrogen dioxide (NO2). The DPF is operative to collect particulate matter in the exhaust gases passing therethrough. International Patent Application Publication No. WO 2008/082492 A2 discloses a method and apparatus for heating exhaust gases of a diesel engine to support regeneration of an exhaust aftertreatment device while simultaneously cooling exhaust gases before passing to the atmosphere.
Although diesel particulate filters are effective in reducing particulate emissions emitted from diesel engines into the atmosphere, diesel particulate filters must be periodically subjected to a regeneration process to burn off the collected particulate matter in order to maintain the particulate removal effectiveness.